1. Field of the Invention
The present invention relates to the structure of a mount mounted in the engine room of a vehicle to support the weight of an engine and dampen vibration, and more particularly, to the structure of an active mount in which damping characteristics are varied when power is applied thereto, the structure of the active mount improving the performance of an actuator that is capable of generating vibrations or controlling the volume of a liquid chamber.
2. Description of Related Art
Not only does an engine of a vehicle always vibrate structurally, the engine also vibrates due to undulations on the ground while the vehicle travels. These vibrations do not act alone, but in combination with various other factors in vertical, lateral, and forward and rearward directions.
Moreover, an engine is not mounted separately from a vehicle body and is connected to a transmission device, a duct system, etc., of the vehicle, so that vibrations generated by the engine affect the entire vehicle.
Therefore, in order to dampen vibrations generated by an engine, the engine is mounted on a vehicle body through an (engine) mount. The mount generally used is a rubber type employing the resilience of the material, or a liquid filled type that is filled with hydraulic fluid and uses viscosity according to the movement of the hydraulic fluid to dampen vibrations.
From thereamong, the liquid filled type mount is referred to as a hydromount which can dampen vibrations over a broader range and is widely used in many types of vehicles.
The hydromount has a structure in which an insulator of a resilient material and an orifice plate are coupled to a cup-shaped housing, and has an inside partitioned into an upper liquid chamber and a lower liquid chamber that are filled with a certain amount of hydraulic fluid. The orifice plate is vertically open and has an annular flow path formed along the perimeter thereof, and is configured to move hydraulic fluid in the upper liquid chamber and the lower liquid chamber by means of resilient compression of the insulator.
In order for an electronic control unit (ECU) of a vehicle to more actively control the damping function of a mount according to the travelling conditions of the vehicle and the operation of the engine, active mounts are being developed that are equipped with electronic or power actuators capable of generating vibrations or adjusting the volume of liquid chambers in hydromounts.
The active mounts have been developed to control the amount of damping according to a predetermined algorithm, on the basis of information and acceleration signals on a vehicle's engine and operating state, in order to operate while providing the optimum amount of damping in situations such as when the vehicle is idling, traveling at low speeds, travelling at high speeds, and turning.
While various structures of active mounts are being developed, to describe one related art technology with reference to FIG. 1, like a typical hydromount, an active mount is configured with an upper liquid chamber and lower liquid chamber partitioned by an orifice plate, the hydraulic fluid being made to flow by means of resilient compression (and/or vibration) of the insulator (generated by the input of vibrations from an engine coupled with a center bolt), and also configured with an actuator for generating vibrations or changing the volume of the liquid chambers to dampen the input vibrations. That is, an actuating plate made of a resilient material is coupled to the orifice plate, and a plunger is further installed to vibrate the actuator plate. An actuator, formed with a coil or the like for generating electromagnetic force to enable the plunger to be pulled by attracting force, is further installed.
The actuator vibrates the plunger at the same phase as the vibration input into the mount so as to improve the damping rate for the vibration transmitted to the vehicle body. The operating principle of this plunger vibration is the repeated process of generating attracting force to move the plunger downward when electric power is applied to an electronic actuator, and of removing the attracting force and restoring the plunger to the original position by means of the restorative force of the actuating plate rubber that was resiliently deformed by the plunger moving downward, when the applied power is turned off.
As illustrated, the actuator has a structure in which an armature and a coil are additionally installed toward the bottom of the plunger so as to apply electromagnetic force (attracting force) in a direction toward the bottom of the plunger, by means of applying an electric current. Thus, the actuating plate is resiliently expanded when the plunger is moved by means of the electromagnetic force, so that when current to the coil is applied and turned off repeatedly, the plunger may be vibrated by being moved and restored to the original position thereof by means of the electromagnetic force and the resilience of the actuator plate.
As described above, an active mount in the related art has limitations in terms of response speed due to the number of vibrations and amplitude that can be generated by using the resilience of an actuating plate material as restorative force.
Further, the precise control of actuator plate displacement with a contactless method using electromagnetic force is difficult, and unintended vibration noise may be generated by the free vibration of the actuating plate from after the resilient restoring of the actuating plate to before the application of electric power to the actuator. In addition, this noise is the cause for reducing vibration insulation performance. Moreover, the structure is one in which the plunger moves downward from an original position and then returns to the original position, so that the rate of change in volume (of a liquid chamber) is low, which has a structural limitation on controlling performance.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.